This invention relates to small-sized electronic devices having depth gauges, in particular, small-sized electronic devices having water depth measuring circuits and which are capable of determining a mean dive depth.
Modern divers dive utilize a variety of devices to ensure safety. One such device is a depth gauge. Small-sized electronic devices which include a depth gauge are known from Japanese Patent Application Laid-Open No. 62-21031 which discloses a scuba diver's watch having a semiconductor pressure sensor unit built within the watch casing. A device within the watch measures depth and counts dive time and displays this data to allow the diver to ascertain diving circumstances, thereby making safe diving possible. Although the conventional small-sized electronic device can measure dive depth and dive time, these two bits of information alone do not completely remove the danger of diver's paralysis, i.e. the "bends".
Over the millennia, human beings have physiologically adapted to normally operate within an environment of one atmosphere of pressure. Accordingly, there are no physiological problems when functioning at an altitude of approximately sea level, where an air pressure of approximately 1 atmosphere is present. However, when mountain climbing or travelling by air, difficulties are encountered caused by air pressure reduction. Similarly, if during scuba diving, the diver ascends too quickly, decompression occurs too quickly and the diver increases the danger of having the bends. This disease occurs if a diver having been subjected to a certain pressure experiences quick pressure reduction so that the equilibrium in pressure within the body of the diver and the environment no longer exists.
Some of these other devices provide more than water depth measurement and included functions for determining maximum water depth, dive time and provide a depth alarm and dive alarm if the dive went to deep or extended the dive for too long a period of time. However, it would still require the diver to predict air supply consumption and control depressurization on the basis of present physical conditions. Furthermore, the knowledge of the diver's physical condition is dependent on the diver's ability to rationally think and calculate based upon ratios of a mean water depth to air consumption and a function of dive time to air consumption. The prior art devices suffer from the disadvantage that they only provided displays of the present and maximum depth. The mean depth was determined based upon the sensibility, coherence and skills of the diver. Accordingly, due to human error, such a calculation is not always accurate leading to unsafe conditions.
Accordingly, it is desired to provide a small-sized electronic device having a depth gauge which overcome the disadvantages of the prior art devices described above by providing a continuous mean water depth display removing the danger of suffering the bends.